Flashback Friday – Lew Harriman & Terry Brennan Mason – EPA Moisture Control Guidance for Design, Construction and Maintenance – Original Air Date: 7-11-2014 | Episode: 333

Air Date: 11-16-2018|Episode 524

This week on Iaqradio+ we flashback to a great show with Lew Harriman and Terry Brennan from 7-11-24. The EPA Moisture Control Guide is one of the best, if not the best document EPA has developed in 20 years. Terry Brennan and Lew Harriman join us to discuss the document and give us their thoughts on evaluating moisture issues in buildings. If you do not have this document in your library, get it, its free and your tax dollars helped to put it together.

Terry Brennan was the lead author for the EPA’s new Guidance for Moisture Control in Buildings. He is a founder and managing partner of Camroden Associates, a building science consulting firm located in Westmoreland, New York. He began his career as a physics major at Northeastern University, but some how, some way got diverted into building science, working on the earliest research into radon problems and radon behavior in buildings, and moving on to energy and moisture issues. For the last 40 years, he’s spent more time crawling around damp basements and hot attics than most normal people would find pleasant. But in return for those decades of investigation, Terry knows a LOT about what makes buildings tick… how they go wrong… and how to make sure they don’t.

Lew Harriman was a contributor to the new EPA guidance for Moisture Control in Buildings on the HVAC aspects of moisture control. He began his career as an architecture student at Dartmouth, but after five years as an Air Force officer, he went to work for a manufacturer of dehumidification systems, and got permanently diverted into HVAC engineering, where he’s spent the last 38 years. He is the founder of Mason-Grant Consulting, a building science consulting firm located in Portsmouth, NH. He is active in ASHRAE as the vice-chair of technical committee 1.12 (Moisture Management in Buildings), and is an ASHRAE Fellow and Distinguished Lecturer.

Z-Man’s Blog:

Moisture Mavens

On Last week’s broadcast of IAQ radio, moisture mavens Terry Brennan and Lew Harriman joined RadioJoe to discuss the EPA’s new guidance document “Moisture Control Guidance for Building Design, Construction & Maintenance”. The guests pointed out that while the EPA’s regulatory and enforcement actions are more obvious to the general public; the agency does valuable work providing guidance on best practices for many important activities that are not currently regulated-such as the removal of mold from buildings.

Terry is the founder and Managing Director at Camroden Associates, Inc. a building science consulting firm. Lew is Director of Research & Consulting at Mason-Grant in Portsmouth, New Hampshire.

History of the development of the document:

The EPA has been aware of moisture problems in buildings for decades. In the 1990s a survey of 100 buildings in different climates found that more than 80% of the buildings had experienced moisture problems at some point during their lives, and 45% had evidence of moisture damage at the time of the survey. Concern over moisture problems in buildings and health effects led to Institute of Medicine (IOM) report and a study at Lawrence Berkeley Lab that found that 20% of asthma can be reasonably attributed to moisture problems in buildings (about 400,000 cases per year in the US.) The EPA’s new “Moisture Control Guidance for Building Design, Construction & Maintenance” book has been 9 years in development. The  document:

  • Sought input from a wide group of contributors and assembled the best practices of how to avoid moisture problems.
  • There is no definition of moisture in the document. ASHRAE is looking at quantifying moisture.
  • Terry was the lead author and Lew was a major contributor. Terry coordinated the input from inside and outside the EPA, and Lew was the “HVAC guy” for the document.
  • The structure of the document is arranged in a practical manner according to phases of construction. Chapter 1 contains a general overview, and is all most building occupants and owners need to know, if their day-to-day responsibilities are not professionally concerned with building design, construction or maintenance. Later chapters focus on: planning, design, construction, operation and maintenance.  Appendices provide checklists for facilities maintenance and operations.
  • According to Lew, it’s a high dew point that causes most problems in buildings rather than high relative humidity. Maintaining a dew point range between 50°F and 60°F will prevent most problems. “Dew point is a more reliable metric than relative humidity.”” Focus on dew point leads to good decisions, while focusing on relative humidity can lead to false alarms or a false sense of security.”
  •  “Pen Test” (penetration test) reveals any physical gaps in the design of air barrier, insulation and/or water barriers. When reviewing the building’s roof, wall and foundation section drawings, it should be possible to trace the continuous line of the sealed water barrier all the way from the roof to the foundation-without ever lifting your pen from the paper. The same must be true for the air barrier and the insulation layer-no gaps, gracks or holes allowed in any of those continuous, sealed layers.
  • Terry’s hierarchy of concerns: 1. Keep rain water out and prevent plumbing leaks. 2. Avoid widespread condensation problems.
  • Lew- ” Humid ventilation and make-up air for building exhaust fans is the single largest source of excess humidity in most commercial and institutional buildings. It’s usually 75 to 90% of the annual dehumidification load. But avoiding problems is easy-during design. Simply grab ALL the ventilation and makeup air and dry it to a dew point below 55°F. Keeping ventilation air dry prevents most problems.  Citing Don Gatley, a building investigator who over the course of his career conducted building inspections in 79 buildings and found that 75 of 79 moisture problems were caused by failing to dry all the ventilation and makeup air-or not drying it deeply enough-or both.
  • Terry- Climate zones seem to be changing. Installing air conditioning into old buildings that formerly didn’t have AC is causing some moisture problems. Outdoor dew points of 70°F+ are a problem when encountered for extended periods of time.
  • Takeaways from the document for Lew Harriman: “there is no federal law that requires you to wear a parachute when jumping out of an airplane.” Similarly, the EPA document is NOT a regulation or a legal requirement, the document IS a set of good ideas and good guidance based on the hard-won experience of dozens of experts that have investigated building moisture problems. EPA was courageous in providing mold cleanup guidance in 2001. This document follows that tradition, by helping everybody avoid mold and moisture problems in the first place
  • According to Lew, even prestigious groups like ASHRAE make mistakes; prior to 1997 ASRAE was focused on designing system for extremes of sensible heat resulting in designs with insufficient dehumidification capacity. For 100 years, ASHRAE overlooked the fact that peak dew points occur at moderate temperatures, and that the peak dew point conditions represent a humidity load that is 40 to 80% higher than at peak temperatures. Since 1997, however, the ASHRAE handbook has contained peak dew point data for more than 8,000 weather stations worldwide. So that’s what engineers should use to design the dehumidification component of any HVAC system.
  • Takeaways from the document for Terry Brennan: 1. Goals as to what to achieve, strategies to achieve the goals, verification that goals have been met. 2. Building envelope commissioning is very useful.(Design and verification of its hygrothermal functions). In particular, avoid rain penetration and condensation within exterior walls and then make sure it drips out, or dries out, when it happens in spite of the designer’s best efforts. Effective flashing is imperative. Water will (sooner or later) drip down through the exterior wall, and gravity isn’t just a good idea, it’s the law. So no missing flashing and no reverse flashing. There are wall assemblies that are known to work well for condensation control in North America . Use what’s been proven successful, modeling a new wall enclosure should not be undertaken lightly. 3. Window manufacturers are publishing instructions for installation and flashing of their product. Follow them. Don’t fall victim of failure of peel and stick flashing due to “installer’s origami skills” or succumb to the temptation to use peel and stick when other methods would be more appropriate and provide superior results. 7. Proper sequencing of installation of air barriers and drainage plane is important. Water drips down-so flashing and water barriers must reflect that fact and be installed in a sequence that prevents trapped water in the walls and under windows.

How to fix moisture problems in existing buildings?

Lew and Terry both say that usually “It ain’t easy and it ain’t cheap” to fix existing buildings that have major problems.

Lew says that the solutions to humidity problems are more obvious when it is understood that the biggest humidity load is coming from incoming ventilation and makeup air. For a start, when the building is NOT occupied, or is lightly occupied, turn off exhaust fans, and reduce or shut off ventilation air. Also, keep air filters clean, otherwise clogged filters cause force the system to pull in air from holes in the envelope instead of through the HVAC system where the incoming air can be dried.

Terry says that with existing buildings,  “Sometimes we need to take the brick off-and that’s a bad day. It’s expensive, and disruptive, and we may find after removing the brick that there is no water barrier behind the brick veneer or the precast exterior cladding.” Then the fixes get really expensive and often exceed owner’s budget and may even exceed the value of the property. When the client can’t afford a permanent and durable solution, sometimes it is necessary to put away “best practices” guidance and make do with less effective but less expensive half-way measures. When eliminating the source of the moisture is economically impractical, one might replace vulnerable materials in damp areas with more moisture-resistant materials, or use an antimicrobial on vulnerable materials that the owner cannot afford to replace.


  • Dew point is of incredible importance. High dew points are a problem.
  • Doesn’t need a committee of 60 people to develop a definition of a damp building. If it’s too damp-you know it’s too damp. 0% moisture content is an impractical goal, and lots of buildings are damp temporarily, which does not lead to problems.
  • No one knows what was done when the building was built.

Final words:

Lew: Agrees with Dieter. Isolated wetting and drying events are not usually a problem. It’s the persistence of dampness and it’s exact location that leads to problems, eg: a spot on a ceiling that represents a stain from a water leak six months ago is no big deal-but active mold growth in a baby’s breathing zone on the wall adjoining his crib is probably a very significant concern.

Terry- EPA doesn’t have funding to print copies of the document, BUT… the document is available as a public service for free download as a PDF file at: http://epa.gov/iaq/moisture/

Today’s Music; “How Dry I Am” by Artie Shaw and his orchestra


Z-Man signing off